Internal pressure piston



Aug. 13, 1940. w. T. CALDWELL 2,211,455

INTERNAL PRESSURE PISTON Filed March 2, 195e INVENTOR AToNEY Patented Aug. 13, 1940 UNITED STATES mais@ 2,211,456 INTERNAL PRESSURE Pls'roN Walter T. Caldwell,

Enid, Okla., assigner to The George E'. Failing Supply Company, Enid, Okla., a corporation of. Oklahoma Application March 2,

Claims.

This invention relates to pistons, particularly those for use in double acting pumps, hydraulic jacks and like devices, and has forits principal objects to provide a piston with a packing element having oppositely directed sealing lips, and to provide a piston equipped with spaced packing elements cooperating to form an annular chamber for containing a lubricant or sealing medium.

It is also an important objectof the invention to provide the packing elements with soft resilient lips which are acted upon by the sealing medium so that when leakage occurs past one of the elements, yielding of the exible lip vthereon imparts pressure upon the sealing medium to enhance sealing engagement of the complementary lip on the other packing element with the wall of the cylinder and vice versa.

A further object of the invention is to provide an improved mounting of the packing elements on the piston rod toV prevent internal leakage through the piston assembly.

In accomplishing these and other objects of the invention, as hereinafter pointed out, I have provided improved details of structure,l the preferred form of which is illustrated in the accompanying drawing, wherein:

Fig. 1 is a longitudinal section through a portion of a pump cylinder or the like equipped with a piston constructed inaccordance with the present invention, the piston also being shown in section.

Fig. 2 is a section-of the parts composing the piston, shown in spaced relation and removed from the cylinder to better illustrate the normal shapes of the packing elements.

Fig. 3 is a perspective view ing elements, a part 'of which is broken away to better illustrate its construction.

Referring more in detail to the drawing:

I designates a portion of a cylinder for a pump, hydraulic jack, or similar device, wherein iluid is acted upon by a piston 2 under high working pressure as in the case of a pump or wherein high pressure duid operates the piston, as in i5 the instance of a hydraulic jack.

Ihe piston 2 is mounted upon a piston rod 3 and includes a pair of ring-like packing elements 4 and 5, each including a hub 6 and 1 carrying peripheral portions 8 of smaller diameter than 0 the cylinder to form a backing for a resilient material 9 that is vulcanized thereto or otherwise attached so that the resilient material forms an integral part of the rings. 'I'he resilient covering 9 for the peripheries 8 is 'of such thickness s as to leave an annular space about-these porof one of the pack- 1938, Serial No. 193,480

tions as shown at l0. The hub B of the ring d has a tapered bore il for engaging a tapered portion l2 of the rod 3, while the hub l of the other ring has a cylindrical bore i3 sleeved over va'reduced'cylindrical extension i4 on the rod. 5 The abutting or facing ends of the hubs are of sufcient length to provide an annular reservoir space between the disk portions 8.

In'order to prevent leakage between the abutting ends of the hubs, the hub t is provided with i@ a bevelled end face l5 that engages within a bevelled recess i6 of the other hub, as clearly shown in Fig. 1. When the rings are in position on the rod, they are retained by a nut il that is mounted on a threaded extension I8 of the cylin- E@ drical end M. The peripheries of the disk portions 8 have laterally extending anges i9 and 20, extending from the respective sides thereof, and which substantially` correspond with the outer shape of the resilient facing and are constructed to enhanceattachment of the facings to the body members of the rings. The resilient material is shaped to provide opposed outwardly flaring sealing lips 2I-22 for the ring l and 23-24 for the ring 5, the lips being slightly com- 25 pressed from peripheral points aligning with the terminal edges of the flanges i9 and 2d when the piston is inserted in the cylinder to sealingly engage with the wall thereof, as` shown in Fig. 1.

'I'he inner or facing lips 22-23 cooperate with 80 the facings on the inner sides of the disk portions to form a lubricant containing chamberl of substantially circular cross-section. 'Ihe lips are reduced in thickness toward the terminal edges thereof so that the edges are extremely exible and movable responsive to pressure imparted upon a lubricant or sealing medium, indicated at 25.

The sealing medium 25 is inserted in the chamber after assembly of the piston and its insertion into the cylinder by way of a channel 26 that is provided in the hub 'l and which normally has, its outer end closed by a plug 2l to retain the lubricant. In order to allow complete lling of the chamber, the disk portion 9 is provided with 45 a vent channel 28 that is normally close/d by a -threaded plug 29. In filling the chamber the plugs are removed and the lubricant or sealing medium is applied by means of a grease gun, or 0 the like, that is connected with the channel 26, the air in the chamber escaping through the other channel 28. A sufficient amount of lubricant or pressure medium is inserted to completely ll the chamberso that yieldability of one of y and 3i, and provided ings 32 and 33 into and through which the resillent material extendsbest shown in Figs. 1 and 'direct action of the pressure medium, 'inner lips 22 and 23 fwith the surface of ner lips aralocated adjacent the sealing medium the lips 22 or 23 will apply sealing pressure on the other lip through the pressure medium.

In order to secure attachment of the resilient facing to the disk portions, the iianges l! and 20 are grooved peripherally as indicated at 2l with series of radial opento form a positive tie, as

It is apparent that should leakage occur past one of the packing rings, the inner flexible lip for that ring will yield to impart pressure on the lubricant which enhances the pressure seal o! the other lip to prevent the leakage from passing from one end of the piston to the other.

In case the piston structure is used in a pump handling gritty materials, such as the drilling uid used in rotary drilling operations, the grit normally tends to work in between the packing rings and the cylinder as the piston is reciprocated therein. A particle of grit or sand tending to pass one of the rings, causes deection of the sealing lip' on the other ring by way of the pressure medium so that it is impossible for the particle of sand or grit to work under the piston. The sand or the like will usually work into the internal pressure chamber and be trapped therein.

The outer` lips 2| and 24 of the respective rings cooperate with the inner lips 22 and 22 toeect seal with the tace of the cylinder. For example,

the outer sealing lips are directly exposed to the pressure medium acting upon the respective ends of the piston so that a primary seal is eiiected by while the are indirectly acted upon by the pressure medium. 'Ihe inner lips are, therefore, protected from abrasive action of any granular material contained 'in the pressure medium and are keptsubstantially clean for contact the cylinder. Since the in- 25, they vxare" adequately lubricated thereby to reduce wear on the piston and cylinder surfaces. K What I clamfand desire to secure by Letters Patent is: Y

'1. A piston4 including a pair oi packing rings each having primary and secondary annular sealing lips, means for retaining said packing rings in concentric alignment with the secondary sealing lips in facing relation, hubs spacing said packing rings to form an annular pressure chamber between said rings, and a pressure transmitting iiuid completely filling the pressure chamber.

2. A piston including a pair of packing rings each having primary andsecondary annular sealing lips, means for retaining said packing rings in concentric augment with the secondary seaiing lips in i'acing relation, l hubs spacing said packing rings to form an annular pressure chamber betweenvsaid rings, and a substantially liquidl sealing medium completely lling said chamber for exerting pressure on the secondary sealins lips.

3. A piston-of the character described including packingvelements having oppositely directed primary and secondary flexible lip portions on each of said elements for engaging the wail of a cylinder and having hub portions for spacing the secondary lip portions to provide a pressure chamber, a pressure transmitting fluid completely lling said chamber, and means for retaining the hub portions of said packing elements in abutting engagement.

4. A piston of the character described including a pair oi packing elements having rigid body portions and primary and secondary iiexible sealing lips adapted for sealingly contacting the surface of a cylinder in which the piston is installed, means spacing said packingelements and cooperating with said secondary sealing lips and surface oi the cylinder to form a confined pressure chamber between said packing elements, and a pressure transmitting iiuid completely iilling said chamber. 2 v

5. A piston of the character'describe'd including a pair of packing elements having rigid body portions and primary and secondary flexible sealinE 'lips adapted for sealingly contacting the suriace of a cylinder in which the piston isinstalled,

means spacing said packing elements and cooperating with said secondary sealing lips and surface of the cylinder to form a coniined pressure chamber between said packing elements, and a liquid completely iilling said chamber.

WALTER T. CALDWELL. 

